Squashed 'bundle/vim-rails/' changes from 1167b39..c2a7b28

c2a7b28 Tab complete generators based on bundled gems
18b05aa Fix formatting
d15ff6b Make :Rails in an app call :Rscript
d26df18 Remove modeline support
8af639d Remove reference to absent URL
4f42820 Remove symbol abbreviations
a57e8bc Fix :Rspec with no arguments

git-subtree-dir: bundle/vim-rails
git-subtree-split: c2a7b284fc63439687c3d81d5825a5f8ad34d27b
Merge commit '6383b641ba383dfd88c63f3f4240a358f99ba13b'